1. Field of the Invention
This invention relates to a vehicle air-conditioning system, specifically a vehicle air-conditioning system using a flammable refrigerant in a refrigerating circuit.
2. Description of the Related Art
The vehicle air-conditioning system of this type has a refrigerating circuit including a refrigerant circulating path, a compressor, a condenser and an evaporator. It is known that use of a flammable refrigerant in place of a chlorofluorocarbon refrigerant contributes much to decrease of burdens on the environment.
However, when the flammable refrigerant is used, a measure against the leak thereof is required. This is because if the flammable refrigerant leaks from a system or a circulating path included in the refrigerating circuit, the risk of the flammable refrigerant catching fire is high. Hence, a technique in which when the leak of the refrigerant from the refrigerating circuit is detected by a sensor, the operation of the compressor is stopped or the circulating path is blocked is disclosed in Japanese Unexamined Patent Publication No. hei 8-178481.
In this type of vehicle air-conditioning system, the evaporator is placed in a vehicle compartment. Specifically, while the compressor and the condenser are placed in an engine room, the evaporator is placed in the vehicle compartment adjacent to the engine room, inside an instrument panel. Since passengers get in and out of the vehicle compartment, not the engine room, as a measure against the leak of the flammable refrigerant, prevention of leak of the refrigerant from the evaporator to the vehicle compartment is particularly essential.
However, if the refrigerant leaks near the evaporator, even if the operation of the compressor is stopped or the circulating path is blocked in the conventional way, the refrigerant near the evaporator can still flow into the vehicle compartment. In other words, the conventional technique still has a problem about ensuring passenger safety.
Further, when the flammable refrigerant is used, attention needs to be paid to problems such as decrease in cooling performance and compressor durability, in addition to ensuring the passenger safety.
This is because, even when prevention of global warming is intended by using the flammable refrigerant, if the energy efficiency of the air-conditioning system is low, it cannot be said that real decrease of burdens on the environment is achieved.